Convert CLI to urfave v2

Followed the Migration Guide at https://cli.urfave.org/migrate-v1-to-v2/
The major changes not pointed out in the migration guide are:
- context.Args() no longer produces a []slice, so context.Args().Slice()
  in substitued
- All cli.Global***** are deprecated (the migration guide is somewhat
  unclear on this)

Signed-off-by: Derek Nola <derek.nola@suse.com>

Vendor in urfave cli/v2

Signed-off-by: Derek Nola <derek.nola@suse.com>

Fix NewStringSlice calls

Signed-off-by: Derek Nola <derek.nola@suse.com>

vendor/github.com/urfave/cli/v2/suggestions.go

@@ -0,0 +1,68 @@
+//go:build !urfave_cli_no_suggest
+// +build !urfave_cli_no_suggest
+
+package cli
+
+import (
+	"fmt"
+
+	"github.com/xrash/smetrics"
+)
+
+func init() {
+	SuggestFlag = suggestFlag
+	SuggestCommand = suggestCommand
+}
+
+func jaroWinkler(a, b string) float64 {
+	// magic values are from https://github.com/xrash/smetrics/blob/039620a656736e6ad994090895784a7af15e0b80/jaro-winkler.go#L8
+	const (
+		boostThreshold = 0.7
+		prefixSize     = 4
+	)
+	return smetrics.JaroWinkler(a, b, boostThreshold, prefixSize)
+}
+
+func suggestFlag(flags []Flag, provided string, hideHelp bool) string {
+	distance := 0.0
+	suggestion := ""
+
+	for _, flag := range flags {
+		flagNames := flag.Names()
+		if !hideHelp && HelpFlag != nil {
+			flagNames = append(flagNames, HelpFlag.Names()...)
+		}
+		for _, name := range flagNames {
+			newDistance := jaroWinkler(name, provided)
+			if newDistance > distance {
+				distance = newDistance
+				suggestion = name
+			}
+		}
+	}
+
+	if len(suggestion) == 1 {
+		suggestion = "-" + suggestion
+	} else if len(suggestion) > 1 {
+		suggestion = "--" + suggestion
+	}
+
+	return suggestion
+}
+
+// suggestCommand takes a list of commands and a provided string to suggest a
+// command name
+func suggestCommand(commands []*Command, provided string) (suggestion string) {
+	distance := 0.0
+	for _, command := range commands {
+		for _, name := range append(command.Names(), helpName, helpAlias) {
+			newDistance := jaroWinkler(name, provided)
+			if newDistance > distance {
+				distance = newDistance
+				suggestion = name
+			}
+		}
+	}
+
+	return fmt.Sprintf(SuggestDidYouMeanTemplate, suggestion)
+}